When you say mirraco, if you're talking about the black label stem, i never had a problem with mine.. if you're referring to those generic (no name) stems they used to put on their completes a couple years back, those are absolute shit..
proper tightening technique is the key to making any stem work flawlessly and last a very long time.. also, with spacers, make sure you don't have too many so that the steerer clamp isn't grabbing tube (no homo, lol).
if you want more rise, there's also the Fit High-Top Stem.. it's pricier, but it gives you 2mm more rise than the freeze and fit stems are magnificent.. the freeze is still perfect and very reliable for the price though.. and considering that 6.35mm is only a quarter of an inch, 2mm isn't even noticeable, but that 49mm reach looks enticing to me though.
Stupidity, outrage, vanity, cruelty, iniquity, bad faith, falsehood - we fail to see the whole array when it is facing in the same direction as we.
-- Jean Rostand